1. Field of the Invention
The invention relates to an improved leaded mounting and connector unit for an electronic device wherein the unit includes a structure having two parallel opposed sides and a plurality of metallized areas which connect with spaced metallized areas provided at the parallel sides to which terminal leads are bonded.
2. Description of the Prior Art
Leaded mounting and connector units for electronic devices are known which are formed from two or more sheets of ceramic particulate, hereinafter referred to as green ceramic sheets, wherein at least one of the sheets have metallized areas. A portion of the metallized areas, which are first plated so conductors can be bonded to it, are used for making connections with an electronic device(s) when it is mounted on the unit with such portions connecting with metallized portions that extend to various edge portions of the sheet. The metallized portions can be on one or more of the sheets. Prior to firing for densification of the sheets, selected spaced areas along the edges of some of the sheets are metallized to make electrical contact with selected metallized areas carried on the major surface of a ceramic green sheet which extend to the edge of the sheet. Such sheets are usually first superimposed on one another in a desired order and the selected edge portions then metallized. Any other additional green ceramic sheets required for the unit are then superimposed on the other sheets and the layered structure is laminated by pressure or pressure and heat prior to heating to densify the ceramic to form a monolithic structure. Leaded mounting and connector units of the type, commonly referred to as side brazed dual in-line units, have been made in this manner. The edge portions of the sheets that receive the metallization in such prior art units present essentially flat side walls. The edge metallized areas are spaced apart in accordance with industry standards. In order to provide improved braze wetting, the edge metallized areas are plated with an acceptable metal such as nickel. Terminal leads, which are secured together at one end by a tie bar, have a portion at the other end of each lead positioned opposite the end metallized areas when they are secured to the plated metallized portions by brazing. In order to maintain alignment of the leads with respect to the edge metallized portions and eliminate expensive brazing fixtures, the leads are formed from metals having essentially the same coefficient of expansion as the densified ceramic such as an iron-nickel-cobalt alloy known by the tradename "Kovar." Standardization of dual in-line units has required the placement and bonding of a set of terminal leads on one side directly opposite a set of leads bonded on the other side, with the same spacing between the leads of each set. Such placement is made at times by using cross tie bars which extend between the two sets of terminal leads.
The prior art structure presents problems with respect to the control of the width and placement of the edge metallization pattern and expensive lead frames or extensive braze fixtures are required to insure alignment of the leads to both the edge metallization areas and to the opposing row of leads. This makes the brazing operation for securing the terminal leads labor intensive, expensive and creates defects and reduce yields.
Further, such prior art leaded mounting and connector units for electronic devices have only limited circuit packaging density which is provided in those units where more than one electronic device may be mounted on a single unit.